Issue with using so.addParam("allowFullScreen", "true"); and a loader inside flash

Hello. I built an actionscript 3 website for a photographer that has
the logo and navigation in one file called main.fla. This file has a
loader and pulls in other swf files when different items are clicked.
The client wants this site to be full screen, when I add so.addParam
(“allowFullScreen”, “true”); the site starts out working just fine,
however, when I load an image gallery swf into the loader in the
main.fla file, it reverts back to actual size. Do I need to put
something in the code of the main.fla file or the image gallery files?